Hi,
It is normal that HikaShop cancels the order when the amount paid is different than the amount of the order.
This usually happens when the user tried to tamper with the amount, trying to pay less than the total so it's a safeguard to avoid you shipping something for an order not paid with the correct amount.
Now the fact that the amount sent to PayPal doesn't correspond to the total amount:
First, that can only happen if you have the "send order details" setting of the PayPal payment method activated.
If you deactivate it, the PayPal payment plugin will always send the full amount of the order and only that.
If you activate it, the PayPal payment plugin will send all the different amounts of the order and PayPal will recalculate itself the full amount.
So I suppose that there is a problem with the way AWOCoupon adds the coupon to the order which leads to that.
Are you able to reproduce the issue yourself ?
If so, if you create a similar coupon in HikaShop and deactivate AWOCoupon temporarily, do you have the same problem ?
If no, I would recommend contacting the AWOCoupon support.
And make sure that you have it updated. It might actually be something already fixed in AWO.